In the past more than ten years, in order to satisfy rapid increase of mobile communication data and application, a multicarrier transmission technology has been widely used in wideband wireless communication systems. A most outstanding feature of a multicarrier system is that it is able to efficiently improve robustness to multipath channel fading, and has a very high spectral efficiency. Orthogonal frequency division multiplexing (OFDM) is the most popular technology in the multicarrier system, and has been applied to the fourth generation (4G) mobile communication systems, wireless local area networks (WLANs), and digital audio broadcasting (DAB), etc. However, there still exist some drawbacks in the OFDM, such as having very large out-of-band leakage, and being sensitive to subcarrier frequency offset, etc.
The main cause that the OFDM has relatively large out-of-band leakage is that the OFDM adopts rectangular signals as its shaping filter, and a peak value of the first side lobe of the waveform of the rectangular signal is lower than a peak value of the main lobe by 13 dB only, which results in relatively large spectral leakage. In order to lower the spectral leakage, a rectangular filter may be replaced with a filter having smooth edges, such as a cosine filter. However, the spectral efficiency of the filter having smooth edges is lowered while the out-of-band leakage is reduced.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.